A device designed to test the purity of water with the ease and speed of a "Star Trek" doctor diagnosing a disease using a "tricorder" was unveiled Monday at Sandia National Laboratories' branch in Livermore.

If terrorists dump viruses, bacteria or bio-warfare toxins into public water supplies, the deadly agents can be detected within seconds or minutes by the portable, cardinal-colored gadget, which is roughly the size and shape of a pre-cellular-age tabletop phone.

Once perfected, the three-pound, battery-powered device will "increase the safety of our nation's water supply" during the terrorist era, Sandia Vice President Mim John said at a news conference at the nuclear weapons lab.

At the news conference, Energy Department spokesperson Larry Adcock recalled how in 1996, Sandia representatives came to him and said, "We're going to build a tricorder." This was a half-joking allusion to the hand-held "Star Trek" gizmo -- usually used by the gruff starship physician Dr. Leonard McCoy, known as "Bones" and played by DeForest Kelley -- that automatically identified a patient's illness.

Existing municipal water systems can't routinely detect all microbial threats in the water supply. Even routine tests for such threats might take many hours in order for investigators to gather water samples and analyze them in a lab.

Worse, such killer microbes and chemicals consist of molecules that are so small that they might easily slip past reservoirs' hazard detectors.

By contrast, the Micro Chem Lab can spot dangerous molecules consisting of just a few hundred atoms, Sandia officials said at the news conference.

And it can identify them quickly, "in seconds to minutes, faster than existing systems," John said.

Aside from terrorism worries, water purity is a growing international concern because the world's population is growing and its water supply isn't. In developing nations, where epidemic diseases sometimes travel by water, the Sandia device could provide a quick way to test basic purity of local water, officials said.

"Is this any good?" one official at the news conference asked jokingly, waving a bottle of mineral water.

The Micro Chem Lab works partly by exploiting physical principles similar to those used in a now-standard technique for identifying DNA, called gel electrophoresis. In that technique, DNA, which carries a negative electrical charge, migrates through a gelatinous substance toward a positive electrical charge. As the DNA moves along through the gel, it leaves line-like "fingerprints" that identify the DNA's molecular structure.

Likewise, the Micro Chem Lab feeds water samples through extremely thin, hair-like tubes filled with gel. As the samples slip through the gel toward a positive or negative electrical charge, they leave chemical traces of large protein molecules. Different viruses, bacteria and biotoxins are characterized by their abundance of certain proteins. By identifying these "fingerprint" proteins, the device can identify the deadly agents.